The general purpose of this research is to establish electrophysiologic correlates of psychiatric illness. Such correlates may then serve to focus animal research on underlying mechanisms. EEG and evoked response data from 6 to 15 electrode placements are obtained in different clinical groups and analyzed in various ways with computer assistance. Patients are followed through treatment with serial determinations to assess the effects of drugs. Evoked response experimental procedures currently employed include: (1) Recovery functions of cortical responses to stimuli applied to right and left median nerves alternately; in this procedure, interstimulus interval is varied while stimulus intensities are kept uniform. (2) In another recovery procedure, intervals are always 10 msec, but stimulus intensity is varied. (3) Checkerboard patterns are exposed to visual half-fields; these are: )a) briefly flashed; (b) constantly present but reversed in one half-field for stimulation. (4) Vibrational stimuli are generated by piezoelectric reeds. EEGs are subjected to power spectrum analysis and evoked responses are automatically analyzed for amplitud, latency, and wave shape stability, and digitally filtered to determine which frequency components relate to independent criteria. Some recent results of interest are; (1) Schizophrenic patients can be subdivided according to amplitude and variability of somatosensory responses into two groups that differ clinically according to degree of depression and severity of spychotic symptoms, such as bizarreness. (2) Lithium carbonate increases somatosensory amplitude mainly by augmenting 32-250 Hz activity, while amitriptyline reduced amlitude mainly be diminishing 4-30 Hz activity. (3) Checkerboard reversal in one half-field produces bilateral electrical responses, which differ significantly on the two sides of the head; the initial event distributes as a dipole, positive at the cortex contralateral to the stimulus and negative on the ipsilateral hemipshere. (4) Checkerboard flash produced a predominantly contralateral response. (5) EEG amplitudes are greater and frequenciesless in chronic schizophrenics than in normals matched for age and sex.